A tire air pressure surveillance system is provided with air pressure detecting devices disposed in vehicle tires for detecting air pressure in the vehicle tires and for sending air pressure information, and a receiving device for receiving the air pressure information sent from the air pressure detecting devices. The tire air pressure surveillance system monitors air pressure in the vehicle tires based on the air pressure information received by the receiving device, so that the vehicle having air-injection type tires are traveling securely.
In the above-described tire air pressure surveillance system, it is necessary to distinguish whether or not the received air pressure information corresponds to the own vehicle, in order to prevent the air pressure state of the tires of the own vehicle from being mistakenly determined based on the air pressure information from air pressure detecting devices of tires of other vehicles. Moreover, in order to accurately determine the air pressure state in each tire of the own vehicle, it is necessary to distinguish the received air pressure information of each tire.
Therefore, distinguishing information is given to each of the air pressure detecting devices. The distinguishing information of the air pressure detecting devices of the tires of the own vehicle is beforehand registered in the receiving device. Furthermore, the air pressure detecting devices send the air pressure information along with the distinguishing information by radio. By comparing the received distinguishing information and the distinguishing information memorized beforehand in the receiving device, it is determined which tire the air pressure information corresponds to (for example, referring to JP-A-2001-322411).
However, the air pressure information from tires of the other vehicles approaching the own vehicle is also received by the receiving device of the every vehicle, and the comparison of the distinguishing information of the air pressure information between the own vehicle and the other vehicles is also performed by the receiving device. Therefore, a process load of the receiving device is increased when traffic is busy.
In order to decrease the process load of the receiving device, a monitor device can be provided to be separated from the receiving device, for monitoring air pressure based on the air pressure information received by the receiving device. That is, the monitor device monitors the air pressure instead of the receiving device, and thereby the process load of the receiving device is reduced. In this tire air pressure surveillance system, the distinguishing information is beforehand memorized as determination information in the receiving device, and only the air pressure information having the distinguishing information corresponding to the determination information is sent to the monitor device. Therefore, it is necessary to provide a memorizing device in the receiving device for memorizing the determination information beforehand, and thereby cost of the receiving device is increased. Moreover, when a tire is exchanged, it is necessary to memorize the distinguishing information (determination information) of the air pressure detecting device of the new tire, in each receiving device again when multiple receiving devices are provided in the vehicle.